The present invention relates to a process for the selective hydroalkylation of paraffinic hydrocarbons with a hydrocarbon selected from the group consisting of paraffins and olefins in the presence of a catalyst comprising (a) one or more Lewis acids of the formula MX.sub.n where M is selected from Group IIIA, IVB, V or VIB elements of the Periodic Table, X is a halogen, n is the ratio of halogen atoms to atoms of M and varies from 1-8, and (b) a hydrogen halide. The preferred Lewis acid is a metal halide, preferably tantalum pentafluoride, niobium pentafluoride or mixtures thereof. The preferred hydrogen halide is hydrogen fluoride.